From what I've heard from a host of family members who were around at the time, the reaction to the bombing of Hiroshima and Nagasaki was universal jubilation.
Everyone in uniform at the time expected a high probability of death in the coming invasion. They and their loved ones, a group that included nearly everyone in the country, were overjoyed at news of a weapon so powerful it would end the war.
It's only been since the democrat party went crazy with hatred for America that it's become popular to question the morality of America defending itself in the most effective manner available.
Prior to the onset of democrat insanity, which began in the late 60s, criticizing President Truman's decision was the province of lunatics. It still is.